Reports began to surface last week about the rise of cases of the mosquito-born Zika virus in South America, and the associated birth defect microcephaly, which is characterized by smaller brain size and has been detected in as many as 4,000 babies in Brazil. Zika was initially found on U.S. soil in the form of several cases of people infected outside of the country, and most recently, the Centers for Disease Control and Prevention this week confirmed that one person has contracted Zika sexually in Texas.

The Aedes aegypti mosquito that transmits Zika is not endemic to Israel, and to date only one Zika infection has been detected in the Jewish state, in a child that had been on a trip to Colombia. But given that the World Health Organization (WHO) this week declared Zika as a world health emergency, the story has gone viral (pun intended) in the Israeli, American, and international media.

Amid the numerous headlines on Zika, what’s fact and what’s fiction? JNS.org gained some insight from Israeli expert Dr. Hagai Levine, head of the environment and health track at the Hebrew University-Hadassah Medical Center School of Public Health. Levine is also an adjunct professor in preventive medicine at Mount Sinai Hospital in New York City, and from 2009-11 he headed the epidemiology section of the Israel Defense Forces Medical Corps.

In the following interview, Levine also discusses the implications of a newly released study commissioned by the Haifa Municipal Association that showed how Israeli babies born in or near Haifa are being exposed to higher levels of pollution, and are born with below-average weight and head circumference measurements. The study has been criticized by the Israeli Ministry of Health as unnecessarily raising public alarm. What’s the real story? Levine provides an insider’s perspective.

JNS: Not all those who contract the Zika virus experience symptoms. But for those who do, how can they identify that they have this particular disease? Other than fever, what are the symptoms?

Levine: “Most of the infections are asymptomatic. About 20 percent [of those infected] have symptoms such as maculopapular rash…muscular pain, and conjunctivitis (pinkeye). Very rarely, we’ve been seeing Guillain-Barre syndrome, a rare syndrome of muscle weakness that can also lead to paralysis.

“These symptoms are not specific for the disease, but they can make you pay attention [to the possibility of contracting the Zika virus]. Of course, if you are in an endemic area for the Zika virus, and you see many others [infected], or if you are bitten by the mosquito, then you are more likely to think that’s the disease that you have.”

JNS: The well-publicized cause-and-effect relationship between the Zika virus and the microcephaly condition, characterized by abnormally small heads in babies, is not conclusive. What would the medical community need to do to prove the connection?

Levine: “I really think we need to be very careful at this point. People feel sure that there is a cause-and-effect [relationship between these conditions], and we are really not there yet. Our understanding [of Zika] can definitely change over time.

“We have circumstantial evidence from the distribution of microcephaly and the dramatic increase of [Zika] cases, from the changing distribution of the Aedes aegypti mosquitos transmitting the Zika virus, and from reported cases of Zika virus both clinically and in some cases also confirmed in a laboratory. But we don’t know for sure yet the cause of the dramatic increase in microcephaly cases, although it is likely caused by the Zika virus.

“On the other hand, we must take action. The absence of evidence is not the evidence of absence. We cannot refute such an association, so we can do several epidemiological studies. We can measure [Zika] antibodies in groups that were infected and not infected, and see the association with microcephaly both for the babies and the mothers. In addition, we can strengthen surveillance systems both of the mosquitos and of the virus, and of human disease in order to improve our understanding. This is part of strengthening public health infrastructure in general. What this event shows is how important it is to invest in public health resources, human resources and laboratory resources beforehand so we can be prepared.”

JNS: WHO has declared Zika an international public health emergency, like it did last year with Ebola, arguably a much more dangerous disease. Zika has been spreading across South America for some time, as have the associated cases of microcephaly. Why do you think WHO made this decision on Zika now?

Levine: “It will be very, very hard to eliminate or eradicate the Zeka virus. In order to control vector-born diseases you need to control the vector. A vector [for Zika] is an insect that transmits a pathogen from the environment to the host. These days we see a change in the environment, presumably due to the El Niño phenomenon and more largely due to climate change, [which] has led to a change in the mosquito distribution. This, in parallel, has led to the Zika virus distribution, and now we have a huge problem globally. We don’t have any vaccine or drugs for the Zika virus.

“[Unlike with Ebola], the outcome of morbidity and mortality could be very low, but the magnitude of the problem is large. If you have a virus or a disease that is not so lethal, generally speaking it’s harder to get rid of it. If you have a pathogen that kills the host then usually the disease is less transmissible, and then you have higher chances of getting rid of the disease. With Ebola you need direct contact for transmission, so if you isolate all the cases of Ebola you can get rid of Ebola. But with vector-born diseases it’s much harder because you need to treat the source, the mosquitos. The solution is not only medical, but must be a collaboration between many disciplines, environment and health professionals.

“The other issue is that we really need in our global response to think global and act local, to tailor our response to the local situation. We need to get rid of standing water, which is also helpful in the prevention of other vector-born diseases like Dengue or Yellow Fever. But regarding pesticides, we should be very careful because we can solve one problem of controlling the mosquitos by creating another problem of massive pesticide exposure, which will hurt both the ecology and humans. We need to keep it balanced and to check ourselves at every step.”

JNS: Are we actually seeing a larger spread of mosquito-born diseases?

Levine: “We do see it recently…the West Nile virus or the Chikungunya virus spreading to new places. That’s exactly my point. Our solution needs to be general and hopefully help us tackle other vector-born diseases. We definitely see the impact of climate change and globalization, of people and trade moving from place to place, and its impact on health.”

JNS: In the same vein as the connection being made between Zika and microcephaly, is the new Haifa municipal study’s purported finding—the connection of air pollution to smaller head circumference and birth weight in babies—a conclusive one?

Levine: “The published data was very preliminary…and we should really wait to see…[before] we can judge the possible risks and associations. However, we know more and more in recent years, [based on] good studies with good measurements…that air pollution is harmful to health. We know from studies in different places in the world… [that] air pollution causes harm to developing babies, [which] can be manifested as smaller head circumference and smaller birth weight. We still need more information. We need to know when is the critical period [during which the fetus can be most affected], and what are the specific consequences of air pollution that are most harmful.

“The main point that I want to stress is that from the point of view of public health, we want to keep health pollution as low as possible. Clearly air pollution causes damage, but of course from society’s point of view, we need to balance [multiple factors] because we also need industry and transportation, etc.”

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